Prior samplers have been designed with capping and entrance system that melted along with and into the molten material being sampled. This caused a source of undesirable contaminants to flow into the actual sample chamber. The prior method also allowed elements contained in the capping system to cause a diluting effect on similar elements contained in the molten batch material.
The location being sampled may contain extremely low (typically, 10 to 50 ppm) values of certain elements, for example, C, S, Mn, O.sub.2, H and N, that must be accurately analyzed in order to produce a high quality product. At these minute ranges, any outside contamination or dilution can cause a significant error in accurate analysis.
Patents representative of the prior art in this area are as follows:
U.S. Pat. No. 4,428,245, issued Jan. 31, 1984 to Nakamura et al; PA0 U.S. Pat. No. 4,007,641, issued Feb. 15, 1977 to Kelsey; PA0 U.S. Pat. No. 4,557,152, issued Dec. 10, 1985 to Plessers et al; PA0 U.S. Pat. No. 4,646,578, issued Mar. 3, 1987 to Lawrenz et al; PA0 U.S. Pat. No. 4,170,139, issued Oct. 9, 1979 to Narita et al; PA0 U.S. Pat. No. 4,250,753, issued Feb. 17, 1981 to Collins; PA0 U.S. Pat. No. 4,140,019, issued Feb. 20, 1979 to Falk; PA0 U.S. Pat. No. 4,112,772, issued Sept. 12, 1978 to McDevitt; PA0 U.S. Pat. No. 4,037,478, issued July 26, 1977 to Cure; PA0 U.S. Pat. No. 4,002,073, issued Jan. 11, 1977 to Collins; PA0 U.S. Pat. No. 3,332,288, issued July 24, 1967 to Mladenovich; PA0 U.S. Pat. No. 3,693,449, issued Sept. 26, 1972 to Collins; PA0 U.S. Pat. No. 4,051,732, issued Oct. 5, 1979 to Falk; PA0 U.S. Pat. No. 3,859,857, issued Jan. 14, 1975 to Falk;
In my U.S. patent application Serial No. 240,506, entitled "Molten Metal Sampling Device", there is proposed a novel capping and entrance system that very much reduces contamination or dilution of the obtained sample. A cap is provided, which is rapidly released from the sampling device upon immersion in the molten metal, and simply floats away.
However, even with the improvement provided by my earlier invention, there remains a slight risk that small portions from the slag layer can be carried down to the region of the sampling device as the latter is plunged downwardly through the slag.
Accordingly, an object of one aspect of this invention is to further decrease the risk of contamination or dilution of an obtained sample.
In a general way, this object is achieved by providing an additional protective cover around the outside of the sampler, the additional protective cover being of a material which tends to repel slag components. The additional protective cover is a composite unit held together by a suitable clip or wire means, whereby the clip or wire fails upon contact with the molten metal, allowing the components of the additional protective cover to separate and float upwardly. While it may still occur that portions of the slag layer adhere to the outside of the additional protective cover, these same contaminants are carried away from the point of sampling along with the components of the additional protective cover as the latter float upwardly to the surface of the melt.
More particularly, this invention provides a holder for a molten metal sampling device, comprising:
a pipe which is elongated in a given direction, the pipe having an upper portion and a lower portion, the lower portion defining an internal guidance chamber and having an opening lying in a plane making an angle with respect to said given direction, the opening communicating with the guidance chamber, the upper portion being adapted to receive and retain the molten metal sampling device in such a way that molten metal in the guidance chamber can be sampled by the sampling device,
a closure element for said opening, the closure element having a density such that it will seek to float upwardly in molten metal outside the pipe,
and a protective cover enclosing said closure element and a lower part of said pipe, the protective cover having at least two separate parts,
and retaining means for holding the separate parts of the protective cover together around the closure element and the lower part of the pipe, the retaining means being adapted to fail upon contact with the molten metal.